This invention relates generally to booting a computer system.
Modern personal computers typically include a set of built-in software routines called the basic input/output system or "BIOS." The BIOS controls many important functions of the personal computer such as how it interprets key strokes, how it puts characters on the screen, and how it communicates with other devices.
The BIOS typically instructs the computer to test itself every time the user turns it on. To do this, the BIOS uses a power on self test ("POST").
When a personal computer starts, it typically first enters what is called "real mode". The computer accesses a special memory location holding program instructions including a jump instruction pointing to the BIOS code. Initially, the BIOS instructs the system microprocessor to run through all the known components of the system and to determine whether they are operating properly. Next, any expansion boards which have been installed are checked, and thereafter, the microprocessor begins the actual bootup process. During the bootup process, the BIOS code instructs the microprocessor to jump to a section of code instructing the microprocessor how to read the first sector of the system floppy, hard disk drive, or CD-ROM drive. The microprocessor then loads the operating system from the disk to start actual computer operations.
Once the operating system has been loaded and is operating, the BIOS may continue to contribute to the operation of the computer. It may do this through routines that programs can access to facilitate commonplace computer functions, such as reading key strokes, timing events or putting characters on a screen. Through the use of such BIOS routines, programmers can create complex programs without being concerned about these underlying functions.
In Windows.RTM.-based computer operating systems, the Windows.RTM. operating system starts only after a DOS boot sequence is completed. There is typically a time lag between when the user turns the computer on and the time when the Windows.RTM. program takes over.
During this DOS/Windows.RTM. booting sequence, an attached monitor will typically display information concerning the booting sequence, and then indicate (through a Windows.RTM. "splash screen") when the Windows.RTM. operating system is loading.